1. Field of the Invention
The present invention relates to an information recording medium capable of simultaneous recording and reproduction of a plurality of real time data, a method for simultaneous recording and reproduction, and an information recording and reproduction apparatus.
2. Description of the Related Art
One exemplary information recording medium having a sector structure is an optical disc. Recently, the high density and the large capacity features of optical discs have been developed. It is highly desirable to have optical discs capable of recording/reproduction video data using high definition (HD) in addition to the standard definition. A method for simultaneous recording and reproduction called “skip reproduction” in the high definition is being reviewed.
Hereinafter, a method for simultaneous recording and reproduction will be described with reference to FIGS. 5 and 6.
FIG. 5 is a diagram showing a principle of a method for simultaneous recording and reproduction of a plurality of real time data in accordance with a simultaneous recording and reproduction model. FIG. 6 is a diagram showing a simultaneous recording and reproduction model for simultaneous recording and reproduction of two real time data.
The simultaneous recording and reproduction model includes a pickup 64 for recording/reproducing real time data for an information recording medium, an encoder 60 for encoding first real time data, a recording buffer 62 for temporarily storing the encoded first real time data before the first real time data is recorded by the pickup 64, a reproduction buffer 63 for temporarily storing second real time data which is reproduced by the pickup 64, and a decoder 61 for decoding the second real time data which is transferred from the reproduction buffer 63. Herein, “real time data” refers to data including at least one of video data and audio data. An “information recording medium” refers to any type of recording medium such as an optical disc.
FIG. 5 shows a transition of an amount of data in the recording buffer 62 and the reproduction buffer 63 in the simultaneous recording and reproduction model during simultaneous recording and reproduction of real time data A and B.
In the example shown in FIG. 5, while the real time data A is recorded in areas 1, 2, 3 and 4 of an information recording medium, real time data B recorded in areas 5, 6, 7 and 8 of the information recording medium is reproduced. The areas 1, 2, 3 and 4 are allocated as areas in which the real time data A is to be recorded. The areas 5, 6, 7 and 8 are allocated as areas having the real time data B recorded therein.
In FIG. 5, A1 through A7 refer to operations of the pickup 64 moving between areas to be accessed (access operations). It is assumed here that the time required for each of the access operations A1 through A7 is a time period required for the pickup 64 to move between an innermost area and an outermost area of the information recording medium (i.e., the maximum access time Ta). It is also assumed that the data transfer rate between the pickup 64 and the recording buffer 62 and the data transfer rate between the pickup 64 and the reproduction buffer 63 are a constant rate Vt. It is also assumed that the data transfer rate between the encoder 60 and the recording buffer 62 and the data transfer rate between the decoder 61 and the reproduction buffer 63 are a constant rate Vd. In the case where the data to be recorded and reproduced is compressed at a variable rate, Vd is the maximum value of the range in which the rate is variable.
In a recording operation W1, real time data A accumulated in the recording buffer 62 is recorded in the area 1. When the real time data A is recorded to the end of the area 1, the recording buffer 62 is not empty. Therefore, the recording operation of the real time data A is not switched to the reproduction operation of real time data B. After an access operation A1, in a recording operation W2, real time data A accumulated in the recording buffer 62 is recorded in the area 2.
While the recording operation W2 is being executed, the recording buffer 62 becomes empty. As a result, the recording operation of the real time data A is switched to the reproduction operation of the real time data B (access operation A2).
In a reproduction operation R1, the real time data B is read from the area 5 and accumulated in the reproduction buffer 63. When the data is reproduced from the end of the area 5, the reproduction buffer 63 is not full. Therefore, the reproduction operation of the real time data B is not switched to the recording operation of the real time data A. After an access operation A3, in a reproduction operation R2, the real time data B is read from the area 6 and accumulated in the reproduction buffer 63.
While the reproduction operation R2 is being executed, the reproduction buffer 63 becomes full. As a result, the reproduction operation of the real time data B is switched to the recording operation of the real time data A (access operation A4).
Thus, the method of simultaneous recording and reproduction is designed so as to fulfill both (i) the condition that the recording buffer 62 can be made empty by at most one access operation and at most two recording operations and (ii) the condition that the reproduction buffer 63 can be made full by at most one access operation and at most two reproduction operations. Namely, the condition for simultaneous recording and reproduction is to fulfill these two conditions. By fulfilling these two conditions, it is possible to ensure the real time data A is recorded on the information recording medium while reproducing the real time data B recorded on the information recording medium, without causing the recording buffer 62 and the reproduction buffer 63 to overflow, and without causing the recording buffer 62 and the reproduction buffer 63 to underflow.
For example, the above-mentioned condition for simultaneous recording and reproduction can be fulfilled where each of at least one area allocated as an area in which the real time data A is to be recorded has a size of Y or greater, and each of at least one area allocated as an area having the real time data B recorded therein has a size of Y or greater.
Accordingly, the condition for simultaneous recording and reproduction can be fulfilled by searching for at least one unallocated area having a size of Y or greater and allocating the at least one area thus found as an area in which the real time data A is to be recorded. The area for the real time data B is obtained in a similar manner.
In the example shown in FIG. 5, the condition for simultaneous recording and reproduction can be fulfilled where each of the areas 1, 2, 3 and 4 has a size of Y or greater, and each of the areas 5, 6, 7 and 8 has a size of Y or greater. The areas 2 and 3 are a continuous recording area, and the areas 6 and 7 are a continuous reproduction area.
The minimum size Y for each recording area and each reproduction area, and a buffer size B which is required for the recording buffer 62 and the reproduction buffer 63, are obtained by the following expressions.Y=4×Ta×Vd×Vt+(Vt−2×Vd)  Expression (1)B=(4×Ta+Y+Vt)×Vd  Expression (2)
The expression for obtaining the minimum size Y for each recording area and each reproduction area is derived as follows.
During a recording operation of the real time data A, the data in the recording buffer 62 is consumed at the rate Vt−Vd. During an access operation and a reproduction operation of the real time data B, the data in the recording buffer 62 is accumulated at the rate Vd. The amount of data which is consumed from the recording buffer 62 during the recording operation W1, the access operation A1 and the recording operation W2 is equal to the amount of data accumulated in the recording buffer 62 during the access operation A2, the reproduction operation R1, the access operation A3, the reproduction operation R2 and the access operation A4. Accordingly, for simultaneous recording and reproduction of two pieces of real time data, the following expression is satisfied.Y+Vt×(Vt−Vd)−Ta×Vd=(3×Ta+Y+Vt)×Vd  Expression (3)
By modifying Expression (3), the above expression for obtaining the minimum size Y for each recording area and each reproduction area is obtained.
In an information recording medium such as an optical disc, a defective block may be formed during fabricating the optical disc, which is called an “initial defect”. Further, a defective block may occur due to scratches and stains.
It is necessary to record data without any influence from such defective blocks. For example, a skip recording method is used to record video data onto the DVD-RAM disc. The skip recording method records real time data while avoiding defective blocks which are detected in advance or defective blocks which are detected during the recording operation (for example, see Japanese Patent No.3098237).
However, when skip recording is performed in the recording operation for simultaneous recording and reproduction, an appropriate condition is not considered. As a result, in a case where real time data is recorded using the skip recording method, due to a plurality of defective blocks, it is not possible to ensure continuous reproduction without any interruption. The present invention is made to solve such a problem.